1. Field of the Invention
The present invention relates to a semiconductor device, and in particular to a metal-insulator-metal (MIM) capacitor structure that increases capacitance density while keeping the voltage linearity coefficient (VCC) value low.
2. Description of the Related Art
Reduced circuit area is an important concern in microelectronics technology. Integrated circuits continue to increase in circuit density due to the reduced size of circuit components. As more components are incorporated into an integrated circuit, higher performance in the circuit can be achieved. One type circuit component that is increasingly incorporated into integrated circuit designs, such as mixed signal, radio frequency, and analog circuits, is a metal-insulator-metal (MIM) capacitor, which typically includes a stacked arrangement of materials of upper and lower metal electrode plates and an intermediate capacitor dielectric layer.
MIM capacitors in such integrated circuit designs, however, may occupy a large portion of the circuit area. In order to reduce the size of circuit components in the integrated circuit, it is desirable to reduce the circuit area occupied by MIM capacitors. Accordingly, an increase in the capacitance density (fF/μm2) of the capacitor is required, thereby proving a suitable capacitance from the MIM capacitor within a smaller circuit area.
Generally, there are several approaches to increase the capacitance density of the MIM capacitor. For example, use of high dielectric constant (k) dielectric materials, such as silicon nitride or hafnium oxide for a capacitor dielectric layer, reduction of the thickness of the capacitor dielectric layer, or combinations thereof. As capacitance density is increased, however, the voltage linearity coefficient (VCC) value (ppm/V2) tends to increase as well. This is undesirable to mixed signal, radio frequency, and analog circuits because they typically require closer capacitor matching and relatively good voltage linearity (low voltage dependence or low VCC value).
Thus, there exists a need in the art for development of improved MIM capacitors which have a high capacitance density while keeping a relatively low VCC value.